pig-a-back
1. [ adverb ] on a railroad flatcar
Synonyms: pickaback piggyback
Examples:

"the trailer rode piggyback across the country"

2. [ adverb ] on the back or shoulder or astraddle on the hip
Synonyms: pickaback piggyback
Examples:

"she carried her child piggyback"

Similar spelling:   piggyback
  pickaback
  pica-pica